pulse echo instrumentation Flashcards by michelle Lee

what control could you adjust to improve the signal to noise ration on the image?
dynamic range
frame averaging
gray scale map
edge enhancement
receiver gain

frame averaging

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the incoming raw echo signals must be compressed into a smaller dynamic range b/c:
wide DR results in inc display of electronic noise
wide DR does not allow dif. b/w echoes arriving from dif depths
display cannot accommodate wide DR of the incoming signals
existing wide DR significantly slows frame rate
wide DR compromised spatial res

display cannot accommodate wide DR of incoming signals
b/c the DR of the system electronics & display is less than that of the raw echo data, it must be compressed into usable range

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what type of imaging results in selective reception of freq that are 2x that of the transmitted freq?
color doppler
PW
tissue doppler
m-mode
tissue harmonic

tissue harmonics

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technique of frame averaging during real time acquisition is designed to:
reduce random noise
decrease pixel size
redistribute gray scale
enhance spatial res
increase frame rate

reduce random noise
frame averaging (persistence) averages data in pixels over successive frames; slight movements of xducer or patient result in slight changes to specle pattern, so frame avg has the effect of smoothing image to reduce speckle

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selective reception of echoes generated within the body by nonlinear propogation describes:
compound imaging
tissue harmonics
speckle reduction
3d image
tomographic u/s image

tissue harmonic imaging

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a type of sonograpic imaging that transmits two pulses of opposite phase in rapid succession so they can be cancelled upon reception:
pulse inversion harmonics
compound imaging
specle reduction imaging
tomographic imaging
panoramic imaging

pulse inversion harmonics

effective method to filter out the fundamental freq (transmitted freq) and leave only the harmonic freq for display

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what can you do to improve the temporal res?
increase # of focal zones
increase depth
increase sector width
decrease acoustic scan line density
decrease acoustic power output

decrease the acoustic scan line density

which decreases the time required to create the image which results in increased frame rate

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duty factor means:
fraction of time xducer is transmitting
fraction of time xducer is receiving
fraction of time b/w transmitted and received pulse
fraction of time b/w transmitted sound pulses
fraction of time required for round trip travel of sound pulse to 1 cm in tissue

fraction of time xducer is transmitting sound

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electronic steering is most commonly applied to which real time xducers?
annular
sequential linear
mechanical sector
phased
segmental linear

phased array

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which is the best choice to help demonstrate tissue boundaries that are not perpendicular to sound beam?
speckle reducing algorithm
spatial compoounding
persistence
panoramic imaging
TGC

spatical compounding

a method in which sound beam is steered in multiple directions by employing time delays

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what is a disadvantage of a water path scanner?
reduces axial res
beam width perpendicular to image plane is inc, resulting in poor elevational res
bubbles in fluid can inhibit sound transmission in body
useful only with low freq
fluid path inc the MI

bubbles in fluid can inhibit sound transmission in body
although they reduce reverberation from shallow structures; they require vigorous maintenance to keep the fluid path completely filled at all times if only partially filled; air bubbles become trapped b/w xducer and probe

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what scanning mode doesn't rely on principle of echo ranging to determine interface location
m-mode
 transmission
PW
static b-mode
a mode

transmission

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what type of focusing is performed by delay circuitry upon reception?
dynamic receive focusing
elevational focusing
transmit focus
multizone transmit
mech focusing

dynamic receive focusing

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when you select compound imaging which artifact is less likely to be observed
refraction
shadowing 
enhancement 
acoustic speckle
all of the above

all of the above

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what is the typical farm rate for b mode real time imaging
1-9 kHz
10-50 Hz
100-200 MHz
200-300 Hz
.05-.9 Hz

10-50 HZ

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what is the advantage of using a 3d/4d xducer w/ automated sweep compared to traditional xducer w/ freehand sweep
measurement accuracy
spatial res
contrast res
larger field of view
greater scanning flexibility

measurement accuracy

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whats the purpose of pre amplification of incoming signal
to decreased DR of signal
inc echo voltages before noise is induced through cable
reduce sensitivity to side lobes
reduce acoustic imped mismatch b/w the tissue and xducer
compensate for attenuation of beam w/ depth

inc echo volt. before noise is induced through cable

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The wavelength you obtain from an arterial stenosis demonstrates aliasing. if you increase the PRF to eliminate the aliasing, what artifact could be introduced?
multipath reflections
spectrum mirror image
prop speed error
range ambiguity
refraction

range ambiguity

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what system control determines the ant of amplification that occurs in the receiver?
gain
acoustic power output
rectification
PRF 
dynamic range

GAIN

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you are imaging a 3d dataset that has anisotropic res. what does this mean?
spatial res is better than temp res
spatial res is = in all dimensions
contrast res is superior to spatial res
unequal res is present b/w imaging planes
elevation res and contrast res are the same

unequal res is present b/w imaging planes

isotropic res= spatial res is = in all dimesnsions
anisotropic res is the opposite

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what action would decrease frame rate?
inc PRF
inc acoustic scan line density
decrease sector width
decrease number of focal zones
decrease image depth

inc aoustic scan line density

temp res is determined by frame rate. as density of acoustic scan line inc lateral res inc but frame rate dec b/c it takes additional time to perform the pulse-listen sequences.

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what is the typical frame rate for b-mode real time imaging?
1-9 kHz
10-50 Hz
100-200 MHz
200-300 Hz
.05-.9 Hz

10-50 Hz

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if you inc the PRF &amp; leave all other controls unchanged what happens?
lat res will improve
frame rate will inc
frame rate will dec
axial res will improve
freq will inc

frame rate will increase

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in the scan converter, interpolation is performed to:
amplify reflected signal in comparison to background noise
dec dynamic range to a level that can be handled by monitor
amplify weak echo signals from deep structures to compensate for beam attenuation
fill in empty pixels that occur b/w acoustic scan lines
inc number of shades of gray in resulting image

fill in empty pixels that occur b/w acoustic scan lines
interpolation is necessary b/c there is not data available for all pixels in the scan converter matrix. as line density dec, more interpolation is needed to fill empty spaces

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``` frame averaging during imaging is designed to: reduce random noise dec pixel size redistribute gray scale enhance spatial res inc frame rate ```

reduce random noise aka persistence avgs the data in pixels over successive frames; it smoothes the image or reduces speckle

``` what can you do to improve temp res? inc number of focal zones inc depth inc sector width dec acoustic scan line density dec acoustic power output ```

dec acoustic scan line density this dec the time required to create the image which increases the frame rate

``` you are manipulating a vol dataset that was previously obtained on your pt. what is the max number of imaging planes that can be obtained ? 1 10 100 1000 there is no limit ```

there is no limit | vol. datasets can be manipulated to show an infinite number of imaging planes w/ many diff. images

``` you are imaging a fluid filled structure w/ equidistant horizontal bands appearing in the near field. they have decreasing brightness with depth. what artifact is this? slice thickness side lobes reverberation comet tail ring down ```

reverberation

``` what adjustment inc the DUTY FACTOR? inc receiver gain inc output power inc PRF inc scanning time inc TGC ```

inc PRF PRF= number of pulses emitted in 1 sec DF= percentage of time that the u/s is being transmitted as PRF inc, percentage of time the u/s is "on" inc.

``` when inc scanning depth, which is automatically dec by the system to avoid range ambiguity? number of focal zones sector width PRF PRP PD ```

PRF

``` what artifact is from an array xducer due to energy that propagates from the xducer in a direction diff from the primary beam? grating lobe mirror image reverberation range ambiguity acoustic enhancement ```

grating lobe | they are the same as side lobes but occur only with array xducers.

``` what artifact is the result of reverberation? comet tail acoustic speckle beamwidth refraction all of the above ```

comet tail | common with metallic objects; occurs when sound bounces back and forth multiple times b/w two interfaces

``` what control can improve signal to noise ratio? dynamic range frame averaging gray scale map edge enhancement receiver gain ```

frame averaging

the range equation describes the relationship b/w: acoustic impede of 2 media side lobe intensity b/w two crystals round trip pulse travel time & dist to reflector bandwidth & xducer freq all of the above

round trip pulse travel time & dist to reflector

``` what effect will you see if you inc reject level? inc # of shades of gray dec low level echoes dec frame rate dec scanning depth dec amplitude of brightest shade of gray ```

dec low level echoes | rejection is used to eliminate weak echo signals from display

``` which display mode is used to calculate dist measurements? a mode b mode m mode b-mode & m-mode all of the above ```

all of the above

``` the range equation is used to determine: reflector amplitude reflector freq reflector direction reflector depth reflector size ```

reflector depth range equation: d=1/2 ct d=depth c=speed of sound in tissue t=round trip travel time

``` what advantage comes from using tissue harmonics? improved contrast res improved penetration improved temp res improved signal to noise ratio increased bandwidth ```

improve contrast res

``` you inc imaging depth and scan line density. what does this result in? reduced contrast res reduced temp res improved axial res reduced lat res all of the above ```

reduced temp res

``` what is not a function of the receiver: amplification rf to video conversion demodulation dynamic aperture compression ```

dynamic aperture | it occurs in beam former and pulser

``` what mode does not rely on echo ranging to determine interface location? mmode PW static b mode transmission b mode ```

transmission

``` number of images displayed per second in real time imaging: PRF PRP frame rate PD pulse length ```

frame rate

``` what physical concept allows us to determine location of an interface by measuring the elapsed time b/w transmitted pulse u/s wave and detected echo? huygens principle shells law doppler effect echo ranging none of the above ```

echo ranging

``` what technique would be most likely to produce grating lobes? tomographic u/s imaging 3d imaging beam steering speckle reduction imaging tissue harmonic imaging ```

beam steering

using a xducer that produces a beam w/ very wide slice thickness. what problem might you encounter? decreased penetration partial volume artifact increased near field reverberations in fluid structures side lobes decreased frame rate

partial volume artifact | aka slick thickness artifact

``` what system function is limited by the speed of sound in tissue? demodulation voltage amplitude PRF rectification TGC ```

PRF

which of the following describes an analog signal? discrete values fixed steps b/w values levels are determined by bits no analog signals exist in modern instruments continuous variation of the signal is possible

continuous variation of the signal is possible

``` what is an advantage of a water path scanner? penetration inc temp res is improved near field reverberations reduced axial res improved slice thickness reduced ```

near field reverberations are reduced

performing a 3d sonogram and volume rate is 8 Hz what does this mean? number of volumes displayed per sec number of transmitted sound pulses per sec number of received pulses per min number of frames per vol number of frames per sec

number of volumes displayed per sec

``` what component of the u/s system converts electric energy provided by pulser into acoustic pulses transmitted into patient? transducer receiver scan converter memory display ```

transducer

``` what is the main advantage of having a thin slice over image plane? imrpoved frame rate better axial res dec vol avg larger field of view greater penetration ```

decreased volume averaging

``` what effect will you detect in the image if you inc the threshold? inc image brightness dec image brightness inc appearance of strong echo signals dec appearance of weak echo signals dec appearance of strong echo signals ```

dec appearance of weak echo signals

``` which of the following helps improve lateral res in b-mode? inc bandwidth focusing with an acoustic lens inc aperture inc dynamic range beam steering ```

inc aperture

``` you obtain 3d sweep in axial plane are are viewing it in multi planar display. what orthogonal planes are displayed? transverse and coronal transverse and sagittal oblique planes at 90 degrees coronal and sagittal oblique planes at 60 degrees ```

coronal and sagittal

``` which of the following helps to improve the elevation res in b mode? inc transmit power focusing with acoustic lens inc bandwidth inc dynamic range beam steering ```

focusing with acoustic lens

``` which artifact commonly results in echoes filling lumen of small vessels? refraction mirror image partial volume range ambiguity multipath ```

partial volume

``` which artifact results in axial and lateral displacement of a reflector? multipath reflections refraction side lobe partial volume enhancement ```

multipath

``` what type of res is determined by number of pixels in scan converter? spatial temporal contrast elevational all of the above ```

spatial | number of pixels inc, spatial res improves.

``` which artifact is related to beam attenuation comet tail enhancement aliasing reverberation side lobe ```

enhancement | enhancement occurs distal to a structure that has less attenuation of the sound beam compared to surrounding tissue

``` improve border definition by ? use lower line density use spatial compound imaging use 2d array transducer apply speckle reduction algorithm use frame avg ```

use spatial compound imaging

``` propagation speed error results in: improper axial pos of echo improper lateral pos of echo shadowing behind echo enhancement behind echo none of the above ```

improper axial pos of echo

``` you are observing sonographic artifact ased on interference patterns of scattered echoes: mirror acoustic speckle grating lobe comet tail refraction ```

acoustic speckle

``` complete destructive interference of echo reflections will affect the display in the following way: white pixel dark gray pixel black pixel light gray pixel none of the above ```

black pixel

``` inc both imaging depth and scan line density results in: reduced contrast res improved axial res reduced temp res reduced lateral res all of the above ```

reduced temporal res greater imaging depth and scan line density decreased the frame rate; axial and contrast res are not affected; inc scan line density will improve lateral res

``` inc number of acoustic scan lines in one frame improves: lateral res temporal res axial res elevational res contrast res ```

lateral res | number of lines in frame inc, distance b/w lines decreases; reducing the dist improves lateral res

``` what component is necessary for real time b mode scanner but not present in a mode? scan converter clock transmitter transducer receiver ```

scan converter

``` which is the best to demonstrate tissue boundaries that are not perpendicular to sound beam? speckle reducing algorithm persistence spatial compound panoramic imaging tgc ```

spatial compound | method which sound beam is steering in multiple directions by employing time delays